Interacting Galaxies in a Cluster

A NASA Hubble Space Telescope image of a previously unknown small group of galaxies estimated to be three billion light-years away. They existed when the universe was only about 80% its present age.

HST's high resolution reveals that many appear to be interacting and merging galaxies. In many cases, at least one member of each pair is blue in color, indicating active star formation, possibly triggered by interaction with a neighbor galaxy.

The observations promise to eventually lead to a much dearer understanding of galaxy evolution.

This image is part of a serendipitous sky survey which has been conducted over the past two years by Prof Richard Griffiths and colleagues at Johns Hopkins University, with a team of astronomers in the U.S. and Britain.

The survey is one of several Key Projects for Hubble. In previous images, the deep survey has uncovered a bizarre variety of shapes and structures in distant galaxies, which only previously appeared as fuzzy blobs from ground based telescopes.

Technical Description

The left-hand frame is a composite "true-color' image taken by Prof Rogier Windhorst and colleagues of Arizona State University, using the 90-inch telescope at Steward Observatory, University of Arizona. The right-hand frame is a "true-color" composite of 9 images taken in visible and near infrared light with the Wide Field Camera, in May 1993. Each exposure was about 30 minutes long. The field of view is 44 arc seconds across, corresponding to a span of 600 thousand light-years at the measured distance to the brightest galaxy in the image. The resolution is 0.1 arc seconds, about 10 times better than can be routinely achieved from the ground.